Enterprises engaged in the business of electroplating chrome, nickel and other metals are plagued by residue aqueous solutions of toxic chemical compounds left over after the plating process. Current governmental regulations require that these contaminated aqueous solutions be transported to a remote licensed toxic waste burial site and buried in sealed steel containers. This method of disposing of toxic sludges is time consuming and expensive. Consequently, a need exists for reducing liquid toxic chemical sludges to a dry powdered form that can be buried in plastic bags at a local waste site, thereby avoiding the costs related to disposing of the liquid toxic waste. Specifically, a need exists for an apparatus which can accept toxic chemical wastes in various sludge forms, from hard clay-like substances to viscous liquids, and is capable of dehydrating said substances to a dry powdered form.
Various furnaces for drying or dessicating materials are well known in the art. Certain of these devices, such as U.S. Pat. Nos. 536,277 to Forrester, 511,184 to Anderson, and 1,008,256 to Gnadt contemplate transporting the material to be dried through a furnace heated pipe by means of a rotating auger, said pipe being substantially horizontal and open at both ends to receive wet material and emit the final product. Specifically, they contemplate that the material to be dried be isolated from the hot furnace gases, being heated solely by conduction of heat from said furnace gase to the material through the pipe wall itself. In each of these references the speed of the auger determines the amount of time the wet material is exposed to the heat of the furnace.
Further, the prior art includes devices for roasting vegetable materials, such as U.S. Pat. No. 2,644,681 to Scull, II, et al. Similarly, Scull teaches the transportation of the material to be dried through a closed conduit by means of a rotating auger. The wet material is heated by the walls of the closed conduit by hot furnace gases passing around it on their way to an exhaust vent.
The prior art also teaches the use of auger driven ovens for various metallurgical smelting operations. In particular, U.S. Pat. No. 415,186 to Bartlett teaches the use of such apparatus for refining lead, zinc and antimony ore by smelting, and U.S. Pat. No. 1,256,703 to Landers teaches the removal of mercury vapor by a continuous retort formed by a similar device. Each of these references teaches the use of a retort containing a rotating auger to drive the ore material to be reacted or smelted through a heated zone where said material is isolated from the hot furnace gases by the retort wall.
Modern calciners as taught by U.S. Pat. Nos. 4,222,987 to Keller and 4,430,057 to Hoover, et al. teach the use of a muffle to isolate the rotating augers containing the material to be reacted or dehydrated from the heat source, typically gas-fired burners. Hoover, et al. also teaches a calcining furnace without a muffle, however, the typical prior art reaction or drying tube must be isolated from the hot furnace gasses to prevent chemical reactions or other interaction between the material being dried or smelted and the flue gasses themselves. This is particularly true when food is being processed, ores smelted, or anytime oxidation of the material is a potential problem.
The prior art teaches the feeding of an oven by use of a hopper mounted at the feed end of said oven and located to allow the oven's auger to pick up the material to be dried or reacted. Typically, arrangements are shown by U.S. Pat. Nos. 1,256,703 to Landers and 1,270,307 to Leyes. A problem experienced when feeding a viscous clay-like sludge through an auger mechanism by means of a hopper occurs where the auger tunnels into the sludge and the remaining sludge collapses slowly into the auger's path, or refuses to do so at all, interrupting the delivery of sludge. Consequently, a need exists in the art for wiping the interior of a hopper and forcing a viscous sludge into the path of an auger so that it may be transported and fed into the input of a dehydrating furnace.